IPhone not even a phone!!!

My iPhone’s mic stopped working. Take it in to three service centres they say the new iOS11.4 update caused the issue I must wait for the new update. In the meantime my phone is absolutely useless for it’s intended purpose. I can’t make or receive phone calls!! Try to talk to apple support online they aren’t even aware of the issue refer me back to service center where I was. When I told them this they gave me another email addres on which no one responds! Don’t get an IPhone people!!